Space discharge device



Dec. 15, 1936. QNEILL 2,064,216

SPACE DI SCHARGE DEVICE Filed Mardh 26. 1935 INVENTOR ATTORNEY Patented Dec. 15, 1936 UNITED STATES 2,064,216 I SPACE DISCHARGE DEVICE George Dean ONeill, Beverly, Mass, assignor to Hygrade Sylvania Corporation, Salem, Mass, a corporation of Massachusetts Application March 26, 1935, Serial No. 13,048

9 Claims.

This invention relates to space discharge devices and more particularly to tubes having relatively small electrode surfaces.

In certain types of radio tubes, for example in so-called low-drop rectifier tubes and the like,

the anode relatively closely surrounds the cathode. When the anode of such a tube is to be heated by electromagnetic induction there exists very low mutual induction between the inducing coil and the anode with the result that so-called bombarding coils used on ordinary radio tubes are impractical or extremely inefficient.

Accordingly, it is a principal object of this invention to provide a tube having a plate or anode with a relatively small electron-receiving surface, which nevertheless can be heated expeditiously by the high frequency bombarding coil customarily used for this purpose.

Another object of the invention is to improve the operating efiiciency of a space discharge tube having an anode with relatively small electronreceiving area, by increasing the radiating surface of the anode without increasing the electron-receiving surface of the anode.

A feature of the invention relates to an anode for radio tubes consisting of a closed tubular portion forming an electron discharge chamber and an enlarged loop portion for improving the exhaust schedule of the tube and for increasing the heat radiating powers of the tube.

Other objects and advantages of the invention not specifically enumerated will be apparent after a consideration of the following detailed description and the appended claims.

While the invention will be described herein as embodied in one particular type of radio tube, it will be understood that this is done merely for purposes of explanation and not by way of limitation.

Accordingly in the drawing, Fig. 1 is an elevational view, partly in section, of a tube embodying features of the invention.

Fig. 2 is a top plan view of the electrode arrangement of the tube of Fig. 1.

Fig. 3 shows a modification of the invention.

Referring more particularly to Fig. l, the numeral I represents in dotted outline, a typical form of glass enclosing envelope such as is in common use in radio tubes or the like. The en- 50 velope I is provided with a reentrant stem portion 2, terminating in a press 3, into which are sealed the lead-in and support wires 4, 5, 6, I, 8. The Wires 4 and 5 are adapted to support the plate or anode. Mounted within the anode is any well-known form of electron-emitting cathode and while the drawing shows a cathode of the so-called indirectly heated type, a filamentary or other type of cathode may be empowered. The cathode as shown may comprise a metal sleeve Ilihaving on its outer surface an electronemissive coating to which connection is made through the lead wire 6. Insulatingly supported within the sleeve It in any well-known manner is a heater filament II. Fastened to the uprights 4 and 5 is an insulator disc I2 preferably of mica or similar material and supported in said disc are free-ended spring wires I3, I4, adapted to engage flexibly the inner wall of the tube I to steady the electrode assembly. The mica disc I2 is provided with a perforation to receive the upper end I5 of the cathode thus centering the cathode with respect to the anode. For a detailed description of the manner of supporting and spacing the electrodes, reference may be had to application Serial No. 721,286 filed Apr. 19, 1934.

In accordance with the present invention the anode I6 is formed with a cylindrical tubular portion which is adaptedto concentrically surround the cathode Ill. The tubular anode I6 therefore defines the electron discharge chamber of the tube in the sense that the electrons from the cathode II] are received only on the inner surface of the tubular anode I6. Because of the relatively small diameter'of the anode I6, it has been found that the ordinary bombarding coil is unsuitable for heating the anode to the proper outgassing temperature. The important factor in driving occluded gases from a metal body such as an anode or other electrode is the ultimate temperature which can be attained by the electromagnetic induction from the bombarding coil. This temperature is dependent among other things upon the magnitude of the current in the bombarding coil, the frequency of this current, and the mutual induction between the coil and electrode. The characteristics of the coil and the frequency of the current are more or less fixed and the current magnitude in the coil must be limited to a practical value. In accordance with this invention the mutual inductance between the coil and electrode is increased without varying the frequency or magnitude of the coil current. One manner of accomplishing this is illustrated in Figs. 1 and 2 of the drawing wherein the anode I6 is provided with laterally extending fin portions II, I8, which in turn are united to a semi-cylindrical wall I9. While the fin portions II, I8, may be separate pieces welded or otherwise fastened to the anode |6 and while the semi-cylindrical wall l9 may also be a separate piece welded or otherwise fastened to the fins I1 and I8, if desired the members l6, l1, l8 and I9 may be formed out of a single strip of metal. Thus as shown in Fig. 2 a single strip of metal is formed with one end 2| having semi-cylindrical off-sets 22, 23, 24. The other end 25 of this same strip is likewise provided with semi-cylindrical offsets 26, 21, 28 and the remainder of the strip is formed into a semi-cylindrical wall I9. The ends 2| and 25 lap over each other so that the off-sets 22 and 28 define a passage to receive the support wire 5. Likewise the ofi-sets 24 and 2B register with each other to receive the support wire 4, and the off-sets 23 and 21 also register with each other to define the electron discharge chamber l6. Preferably the lapped portions 2| and 25 are welded or otherwise fastened together at various points to form in effect a rigid body of metal. There is thus provided a completely closed tubular anode, the inner surface of which acts to receive the electrons from the cathode |U while the lateral portions and semi-cylindrical portion I9 form a closed loop of very large area as compared with the area of the anode proper. Consequently when the tube I is to be evacuated the very large area formed by the members I9, 2| and 25 enables the usual bombarding coil to be employed to bring the anode up to the required temperature in an expeditious manner. Furthermore when the tube is in actual use the portions I9, 2| and 25 provide relatively large heat radiating surfaces for the anode l6.

Instead of making the wall l9 semi-cylindrical as in Figs. 1 and 2, this wall may be made cylindrical. Thus as shown in Fig. 3 the anode may consist of two metal strips 3|, 35 having aligned off-set portions to define cylindrical spaces 32, 33, 34. The metal bounding the space 33 is adapted to function as the anode and defines the electron discharge space similarly to the anode l6 of Fig. 1, while the spaces 32 and 34 are adapted to receive support rods similar to rods 4 and 5 of Fig. l. The portion 35 in this embodiment however is of circular cylindrical formation and is fastened, as by welding, to portion 3|. The portion 35 may be provided with one or more off-sets 36 to receive additional support rods.

While specific shapes for the anode or electron discharge chamber have been shown, various changes and modifications may be made herein without departing from the spirit and scope of the invention. Furthermore while the invention is of pronounced utility in low-drop rectifier tubes such as shown in Figs. 1 and 2, one or more grids or foraminous electrodes may be interposed between the cathode and anode as indicated by numeral 31 (Fig. 3). The anode and curved extension may be of any metal ordinarily employed for the anodes of discharge tubes, preferably however the metal has its surface blackened as by carbonizing to increase its heat radiating powers.

What I claim is:

1. A space discharge tube having an electronemitting cathode, a tubular anode forming a closed loop surrounding said cathode, and a curved conducting wall forming a second closed loop, said anode being interposed between the ends of said second loop to complete the same.

2. A space discharge tube having an electronemitting cathode, a tubular anode forming a closed loop surrounding said cathode, and another tubular metal member of materially greater surface area, the said anode and the said member being conductively fastened together so that said anode completes the wall of said tubular member.

3. A space discharge tube having an electronemitting cathode, a metal member having two parallel tubular portions, one of which is closed and surrounds the cathode and the other of which has a surface area larger than the area of the portion surrounding the cathode and forms with the closed portion a separate tubular closed portion.

4. A space discharge tube according to claim 1 in which the tubular anode and the curved wall are formed from a single sheet of metal.

5. An electrode for a space discharge tube comprising a circumferentially complete tubular metal member defining an electron-discharge space, and a curved metal wall member fastened to said tubular member said wall member having a surface area greater than the surface area of said tubular member and forming with the first member a separate complete tubular member.

6. An electrode according to claim 5 in which the said wall member is substantially semicylindrical.

7. An electrode according to claim 5 in which said wall member is substantially cylindrical.

8. An anode electrode for a space discharge tube comprising a tubular member defining an electron discharge space, a pair of lateral fin members extending from said tubular member and a curved wall member having its ends fastened to said fin members and forming with said fin members and said tubular member a separate closed conductive loop of greater peripheral extent than that of the first tubular member.

9. A low drop rectifier tube comprising an electron-emitting cathode, a cylindrical anode surrounding said cathode, and defining a closed loop, a curved wall member of greater surface area than the surface of said anode, said wall member defining with said anode a separate, closed conductive loop.

GEORGE DEAN ONEILL. 

